1. Field of the Invention
The present invention relates to an electronic apparatus capable of detecting a motion vector from a video content, a motion vector detecting method for the electronic apparatus, and a program therefor.
2. Description of the Related Art
In recent years, in electronic apparatuses such as a recording/reproducing apparatus including an HDD (Hard Disk Drive) recorder, a DVD (Digital Versatile Disk) recorder, and a BD (Blu-ray Disc) recorder, and a PC (Personal Computer), capacities of recording media are expanded and amounts of contents to be recorded and stored are increased due to diversification of contents and the like. As one technique to allow users to effectively view such a large amount of contents, there is a technique of detecting a motion feature of a camera (hereinafter, referred to as camera operational feature) (e.g., pan, tilt, and zoom) that has shot a video content, and extracting a feature section within the video content based on the detected feature, to thereby reproduce a highlight scene.
Such a camera operational feature can be detected by detecting a motion vector using block-matching processing. The block-matching processing involves, for example, extracting a basis block from a basis frame within the video content, and moving a retrieval block within a retrieval range in a retrieval frame that has a predetermined frame interval with respect to the basis frame, to retrieve a position at which a similarity degree becomes maximum, that is, a position at which a matching differential becomes minimum.
However, in a case where a camera that has shot the video content is moved fast, for example, the block corresponding to the basis block may be retrieved outside the retrieval range. In this case, because it is difficult to determine if the block corresponding to the basis block is within the retrieval range or outside the retrieval range, when the block corresponding to the basis block is outside the retrieval range, a position at which the similarity degree becomes maximum inside the retrieval range may be detected regardless of the fact that a current movement position is not inside the retrieval range. As a result, a motion vector different from that of the actual movement may be erroneously detected. Further, when a scene change occurs between the basis frame and the retrieval frame, for example, although no motion vector normally exists between both of the frames without doubt, the motion vector may be erroneously detected in this case, too.
Regarding the problems described above, Japanese Patent Application Laid-open No. 2003-299040 (FIG. 6 etc.) (hereinafter, referred to as Patent Document 1) discloses the following technique. In this technique, an absolute differential sum between a basis block cut out from a current frame and a retrieval block that moves within a retrieval range of a reference frame that is one frame after the current frame is calculated, and a pixel position of the retrieval block at which the absolute differential sum becomes minimum is retrieved, to thus obtain a motion vector between a pixel position of the retrieval block and that of the basis block. In this case, when the pixel position at which the absolute differential sum becomes minimum is outside the retrieval range, a vector amount of the obtained motion vector is corrected so that the above-mentioned pixel position is located inside the retrieval range.